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Böhmite

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Formula:
AlO(OH)
System:
Orthorhombic
Colour:
White, pale greyish ...
Hardness:
Name:
For Johann (Johannes, Hans, Jan) Böhm (1895-1952) Czech-German physical-chemist, crystallographer and photographer, who first studied the species.
Dimorph of:
A major constituent of the aluminium ore Bauxite.

Dimorphous with Diaspore and isostructural with Lepidocrocite.

Classification of Böhmite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
4.FE.15

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
F : Hydroxides (without V or U)
E : Hydroxides with OH, without H2O; sheets of edge-sharing octahedra
6.1.2.1

6 : HYDROXIDES AND OXIDES CONTAINING HYDROXYL
1 : XO(OH)
7.6.2

7 : Oxides and Hydroxides
6 : Oxides of Al
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First Recorded Occurrence of Böhmite

Geological Setting of First Recorded Material:
Bauxite deposit
Associated Minerals at First Recorded Locality:

Occurrences of Böhmite

Geological Setting:
In bauxite, laterite or fireclay deposits; as a low-temperature hydrothermal decomposition product in nepheline pegmatites, syenites and ocean-ridge basalts.

Physical Properties of Böhmite

Vitreous, Pearly
Diaphaneity (Transparency):
Translucent
Colour:
White, pale greyish brown; yellowish or reddish when impure; colourless in thin section
Streak:
White
Hardness (Mohs):
Cleavage:
Very Good
on {010}, good on {100}, and poor on {001}
Density:
3.02 - 3.05 g/cm3 (Measured)    3.08 g/cm3 (Calculated)

Crystallography of Böhmite

Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Cell Parameters:
a = 3.693Å, b = 12.221Å, c = 2.865Å
Ratio:
a:b:c = 0.302 : 1 : 0.234
Unit Cell Volume:
V 129.30 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Rarely tabular to stout prismatic crystals, to 2 mm, showing {001}, {110}, {101}, {111}, {221}; commonly extremely fine-grained, in pisolitic aggregates or disseminated.
X-Ray Powder Diffraction Data:
d-spacingIntensity
6.11 (100)
3.15 (60)
2.347 (60)
1.862 (20)
1.850 (20)
1.308 (15)
1.661 (10)
Comments:
Recorded on material from Hurunui Peak, New Zealand

Optical Data of Böhmite

Type:
Biaxial (+)
RI values:
nα = 1.644 - 1.648 nβ = 1.654 - 1.657 nγ = 1.661 - 1.668
2V:
Measured: 74° to 88°, Calculated: 80°
Max Birefringence:
δ = 0.017 - 0.020
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
weak

Chemical Properties of Böhmite

Formula:
AlO(OH)
Essential elements:
All elements listed in formula:
Analytical Data:
(1) Chemical analysis of material from Vishnevy Mts, Urals, Russia
(2) Electron microprobe analysis of material from Hurunui Peak, New Zealand; water content calculated from stoichiometry
         (1)      (2)

SiO2    (2.11)   (0.76)
TiO2             (0.03)
Al2O3  (81.60)  (83.84)
Ga2O3   (0.05)
Fe2O3   (0.58)   (0.53)
MgO              (0.02)
CaO     (0.26)   (0.08)
H2O    (15.31)  (15.05)

sum     99.91   100.31 wt.-%
Empirical Formula:
Al0.98[O0.96(OH)1.04]=2.00 (1); Al0.98Si0.01O(OH) (2)

Relationship of Böhmite to other Species

4.FE.05Amakinite(Fe2+,Mg)(OH)2
4.FE.05BruciteMg(OH)2
4.FE.05PortlanditeCa(OH)2
4.FE.05PyrochroiteMn(OH)2
4.FE.05TheophrastiteNi(OH)2
4.FE.10BayeriteAl(OH)3
4.FE.10DoyleiteAl(OH)3
4.FE.10GibbsiteAl(OH)3
4.FE.10NordstranditeAl(OH)3
4.FE.15Lepidocrociteγ-Fe3+O(OH)
4.FE.20GrimaldiiteCrO(OH)
4.FE.20HeterogeniteCoO(OH)
4.FE.25FeitknechtiteMn3+O(OH)
4.FE.25Lithiophorite(Al,Li)MnO2(OH)2
4.FE.30QuenselitePbMnO2(OH)
4.FE.35FerrihydriteFe103+O14(OH)2
4.FE.40FeroxyhyteFe3+O(OH)
4.FE.40Vernadite(Mn4+,Fe3+,Ca,Na)(O,OH)2 · nH2O
4.FE.45QuetzalcoatliteZn6Cu3(TeO6)2(OH)6 · AgxPbyClx+2y
7.6.1CorundumAl2O3
7.6.2DiasporeAlO(OH)
7.6.4GibbsiteAl(OH)3
7.6.5BayeriteAl(OH)3
7.6.6NordstranditeAl(OH)3
7.6.7DoyleiteAl(OH)3
7.6.8Akdalaite4Al2O3 · H2O

Other Names for Böhmite

Name in Other Languages:
Croatian:Bemit
Danish:Böhmit
French:Boehmite
Italian:Boehmite
Norwegian (Bokmål):Böhmitt
Polish:Bemit
Russian:Бемит
Serbian (Cyrillic Script):Бемит
Simplified Chinese:一水软铝石
勃姆石
Ukrainian:Беміт

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Industrial Uses:
As a constituent of bauxite an important raw material for the industrial production of aluminium.

References for Böhmite

Reference List:
Böhm, J. (1925): Über Aluminium- und Eisenhydroxyde. I. Zeitschrift für anorganische und allgemeine Chemie. 149, 203–216

de Lapparent (1927), Comptes Rendus 184, 1661.

American Mineralogist (1928), 13, 72.

de Lapparent (1930), Bulletin de la Société Minéralogique 53, 262.

Goldstaub (1936), Bulletin de la Société Minéralogique 59, 348.

Palache, C., Berman, H. and Frondel, C. (1944): The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc. (New York), 7th edition, revised and enlarged, 645-646.

Deer, W. A., Howie, R. A. and Zussman, J. (1962): Rock-forming minerals, Vol. 5, Non-silicates, 111-117.

Sahama, T. G., Lehtinen, M. and Rehtijärvi, P. (1973): Natural boehmite single crystals crom Ceylon. Contr. Mineral. Petrol. 39, 171-174.

Shelley, D., Smale, D. and Tulloch, A. J. (1977): Boehmite in syenite from New Zealand. Mineralogical Magazine 41, 398-400.

Kiss, A. B., Keresztury, G., and Farkas, L. (1980): Raman and IR spectra and structure of boehmite (γ-AlOOH). Evidence for the recently discarded D 17 2h space group. Spectrochimica Acta 36A, 653-658.

Larsen, A. O. (1981): Boehmite from syenite pegmatites in the Oslo region, Norway. Mineralogical Record 12, 227-230.

Hill, R. J. (1981): Hydrogen atoms in boehmite: a single crystal X-ray diffraction and molecular orbital study. Clays and Clay Minerals 29, 435-445.

Corbató, C. E., Tettenhorst, R. T. and Christoph, G. G. (1985): Structure refinement of deuterated boehmite. Clays and Clay Minerals 33, 71-75.

Anthony, J. W. et al. (1997): Handbook of Mineralogy, Vol. 3, 70.

Internet Links for Böhmite

Specimens:
The following Böhmite specimens are currently listed for sale on minfind.com.

Localities for Böhmite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
Mineral and/or Locality  
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